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About one-tenth of Earth’s surface is always under the cover of ice. And almost 90 percent of that ice is found in the continent of Antarctica. The remaining 10 percent is found on the mountains in the form of glaciers.

The ice sheet that covers Antarctica is almost one-and-a-half times the size of the United States.

Explosive chemical reactions are what send spacecraft into space. A rocket burns fuel to produce a jet of hot, expanding gas. What fuel is used varies, but whatever the mixture, it causes the explosive chemical reaction.

Because a rocket needs thrust to escape Earth’s gravity, the explosive chemical reaction takes place in a confined chamber and releases gases into a cone-shaped nozzle out the back end of the rocket. The cone shape accelerates the gases and they blast out of the engine at up to 9,941 miles (15,998 kilometers) per hour.

The Joshua tree is a desert tree that grows in southwestern North America, in California, Arizona, Utah, and Nevada. A native of the Mojave Desert, these droughttolerant trees thrive in the open grasslands of California’s Joshua Tree National Park. The Mormon pioneers named this tree after the prophet Joshua, because its extended branches resembled the outstretched arm of Joshua as he pointed with his spear to the ancient city of Ai. The trees are twisted and spiky, with tough leaves, and look a little bit like a tree from a Dr. Seuss book. Joshua trees can grow from seed or from an underground rhizome of another Joshua tree. They grow very slowly, sometimes 3.9 to 7.8 inches (10 to 20 centimeters) in their first few years.

The tallest trees reach about 49 feet (15 meters) tall. The trunk of a Joshua tree is made of thousands of small fibers and does not have yearly growth rings, Which makes it hard for scientists to tell the tree’s age. Although the fragile tree has shallow roots, if it survives the harsh desert environment, it can live hundreds— even thousands—of years.

Located at 0 degrees longitude, the prime meridian passes through Greenwich, England. Halfway around the world in the middle of the Pacific Ocean (180 degrees from Greenwich) is the International Date Line (IDL), where the date changes across the boundary of the time zone.

The entire world is on the same date only at the instant when it is noon in Greenwich, England, and midnight at the IDL. At all other times, there are different dates on each side of the IDL.

Tropical coral reefs are ridgelike or moundlike structures composed of corals and other aquatic organisms. They border the shorelines of more than 100 countries. Although coral reefs comprise less than 0.5 percent of the ocean floor, it is estimated that more than 90 percent of marine species are directly or indirectly dependent on them—they are home to approximately 4,000 species of fish alone.

Reefs protect human populations along coastlines from wave and storm damage by serving as buffers between oceans and near-shore communities. The Great Barrier Reef, located in northeast Australia’s Coral Sea, measures 1,616 miles (2,000 kilometers) in length. It the largest living structure on Earth, and can be seen from the Moon.

1. On average, a man spends about five months of his life shaving.
2. On average, a hair strand’s life span is five and a half years.
3. On average redheads have 90,000 hairs. People with black hair have about 110,000 hairs.
4. Next to bone marrow, hair is the fastest growing tissue in the human body.
5. In a lifetime, an average man will shave 20,000 times.
6. Humans have about the same number of hair follicles as a chimpanzee has.
7. Hair will fall out faster on a person that is on a crash diet.
8. The longest human beard on record is 17.5 feet, held by Hans N. Langseth who was born in Norway in 1846.
9. The average human head weighs about eight pounds.
10. The reason why some people get a cowlick is because the growth of their hair is in a spiral pattern, which causes the hair to either stand straight up, or goes to a certain angle.
11. The reason why hair turns gray as we age is because the pigment cells in the hair follicle start to die, which is responsible for producing “melanin” which gives the hair colour.
12. The fastest growing tissue in the human body is hair.

13. A lifespan of an eyelash is approximately 150 days.
14. A survey done by Clairol 10 years ago came up with 46% of men stating that it was okay to color their hair. Now 66% of men admit to coloring their hair.
15. The big toe is the foot reflexology pressure point for the head.
16. The average human scalp has 100,000 hairs.
17. The first hair dryer was a vacuum cleaner that was used for drying hair.
18. Ancient Egyptians used to think having facial hair was an indication of personal neglect.
19. The loss of eyelashes is referred to as madarosis.
20. Hair and fingernails are made from the same substance, keratin.
21. Eyebrow hair lasts between 3-5 months before it sheds.
22. A Russian man who wore a beard during the time of Peter the Great had to pay a special tax.
23. Everyday approximately 35 meters of hair fiber is produced on the scalp of an adult.
24. Hair is made from the same substance as fingernails.
25. Brylcreem, which was created in 1929, was the first man’s hair product.

Absolutely. Being bitten by a plant-eating dinosaur such as Brachiosaurus, with its 52 chisel-like teeth, would certainly hurt! The bite of a Parasaurolophus, with its interlocking rows of teeth, might take off your fingers. In the Iguanodon, numerous sharp teeth were set in rows in the upper and lower jaws, and at steep angles to each other.

When the teeth were pressed together, the upper jaw was forced outward, creating a grinding motion between the teeth and its meal of crushed plant tissue.

Scientists do not know exactly why people need sleep, but studies show that sleep is necessary for survival. Sleep appears to be necessary for the nervous system to work properly. While too little sleep one night may leave us feeling drowsy and unable to concentrate the next day, a long period of too little sleep leads to poor memory and physical performance.

Quickly gobbling up cold ice cream may result in “brain freeze,” also know as an ice cream headache. When the cold object touches the roof of your mouth, the blood vessels contract in order to prevent loss of body heat. As the coldness stops, the blood vessels relax again, quickly increasing blood flow to the brain.

This sudden release is What causes the intense headache sensation. You can relieve brain freeze by quickly warming the roof of your mouth: Touch your tongue to the top of your mouth or, if you can roll your tongue in a ball, press the underside of your tongue (which is warmer) to the roof of your mouth. Slowly sipping room-temperature water or pressing a warm thumb against the roof of the mouth also works for some people.

Scientists often compare Earth to an onion because the planet is made up of many layers of rocks of different densities. On the outside, there is a think crust of hard, cold rock, which is about 4 miles (7 kilometers) thick under the oceans and 22 miles (35 kilometers) thick under the continents. The crust—the layer we live on—surrounds a hard, rocky surface that marks the top of the mantle, called the lithosphere. Most of Earth is made of its mantle, Which goes almost halfway down to Earth’s center.

At the very center is Earth’s core, which has a center of solid iron and nickel about the size of the Moon (called the inner core) and a molten exterior (called the outer core). The temperature of Earth increases about 36 degrees Fahrenheit (2.2 degrees Celsius) for every 0.62 miles (1 kilometer) down you go, reaching temperatures as high as 11,000 degrees Fahrenheit (6,093 degrees Celsius) at its center.